arch: Remove Itanium (IA-64) architecture

The Itanium architecture is obsolete, and an informal survey [0] reveals
that any residual use of Itanium hardware in production is mostly HP-UX
or OpenVMS based. The use of Linux on Itanium appears to be limited to
enthusiasts that occasionally boot a fresh Linux kernel to see whether
things are still working as intended, and perhaps to churn out some
distro packages that are rarely used in practice.

None of the original companies behind Itanium still produce or support
any hardware or software for the architecture, and it is listed as
'Orphaned' in the MAINTAINERS file, as apparently, none of the engineers
that contributed on behalf of those companies (nor anyone else, for that
matter) have been willing to support or maintain the architecture
upstream or even be responsible for applying the odd fix. The Intel
firmware team removed all IA-64 support from the Tianocore/EDK2
reference implementation of EFI in 2018. (Itanium is the original
architecture for which EFI was developed, and the way Linux supports it
deviates significantly from other architectures.) Some distros, such as
Debian and Gentoo, still maintain [unofficial] ia64 ports, but many have
dropped support years ago.

While the argument is being made [1] that there is a 'for the common
good' angle to being able to build and run existing projects such as the
Grid Community Toolkit [2] on Itanium for interoperability testing, the
fact remains that none of those projects are known to be deployed on
Linux/ia64, and very few people actually have access to such a system in
the first place. Even if there were ways imaginable in which Linux/ia64
could be put to good use today, what matters is whether anyone is
actually doing that, and this does not appear to be the case.

There are no emulators widely available, and so boot testing Itanium is
generally infeasible for ordinary contributors. GCC still supports IA-64
but its compile farm [3] no longer has any IA-64 machines. GLIBC would
like to get rid of IA-64 [4] too because it would permit some overdue
code cleanups. In summary, the benefits to the ecosystem of having IA-64
be part of it are mostly theoretical, whereas the maintenance overhead
of keeping it supported is real.

So let's rip off the band aid, and remove the IA-64 arch code entirely.
This follows the timeline proposed by the Debian/ia64 maintainer [5],
which removes support in a controlled manner, leaving IA-64 in a known
good state in the most recent LTS release. Other projects will follow
once the kernel support is removed.

[0] https://lore.kernel.org/all/CAMj1kXFCMh_578jniKpUtx_j8ByHnt=s7S+yQ+vGbKt9ud7+kQ@mail.gmail.com/
[1] https://lore.kernel.org/all/0075883c-7c51-00f5-2c2d-5119c1820410@web.de/
[2] https://gridcf.org/gct-docs/latest/index.html
[3] https://cfarm.tetaneutral.net/machines/list/
[4] https://lore.kernel.org/all/87bkiilpc4.fsf@mid.deneb.enyo.de/
[5] https://lore.kernel.org/all/ff58a3e76e5102c94bb5946d99187b358def688a.camel@physik.fu-berlin.de/

Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 0 insertions, 146 deletions

diff --git a/arch/ia64/include/asm/ptrace.h b/arch/ia64/include/asm/ptrace.h
deleted file mode 100644
index 402874489890..000000000000
--- a/arch/ia64/include/asm/ptrace.h
+++ /dev/null
@@ -1,146 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 1998-2004 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- *	Stephane Eranian <eranian@hpl.hp.com>
- * Copyright (C) 2003 Intel Co
- *	Suresh Siddha <suresh.b.siddha@intel.com>
- *	Fenghua Yu <fenghua.yu@intel.com>
- *	Arun Sharma <arun.sharma@intel.com>
- *
- * 12/07/98	S. Eranian	added pt_regs & switch_stack
- * 12/21/98	D. Mosberger	updated to match latest code
- *  6/17/99	D. Mosberger	added second unat member to "struct switch_stack"
- *
- */
-#ifndef _ASM_IA64_PTRACE_H
-#define _ASM_IA64_PTRACE_H
-
-#ifndef ASM_OFFSETS_C
-#include <asm/asm-offsets.h>
-#endif
-#include <uapi/asm/ptrace.h>
-
-/*
- * Base-2 logarithm of number of pages to allocate per task structure
- * (including register backing store and memory stack):
- */
-#if defined(CONFIG_IA64_PAGE_SIZE_4KB)
-# define KERNEL_STACK_SIZE_ORDER		3
-#elif defined(CONFIG_IA64_PAGE_SIZE_8KB)
-# define KERNEL_STACK_SIZE_ORDER		2
-#elif defined(CONFIG_IA64_PAGE_SIZE_16KB)
-# define KERNEL_STACK_SIZE_ORDER		1
-#else
-# define KERNEL_STACK_SIZE_ORDER		0
-#endif
-
-#define IA64_RBS_OFFSET			((IA64_TASK_SIZE + IA64_THREAD_INFO_SIZE + 31) & ~31)
-#define IA64_STK_OFFSET			((1 << KERNEL_STACK_SIZE_ORDER)*PAGE_SIZE)
-
-#define KERNEL_STACK_SIZE		IA64_STK_OFFSET
-
-#ifndef __ASSEMBLY__
-
-#include <asm/current.h>
-#include <asm/page.h>
-
-/*
- * We use the ia64_psr(regs)->ri to determine which of the three
- * instructions in bundle (16 bytes) took the sample. Generate
- * the canonical representation by adding to instruction pointer.
- */
-# define instruction_pointer(regs) ((regs)->cr_iip + ia64_psr(regs)->ri)
-# define instruction_pointer_set(regs, val)	\
-({						\
-	ia64_psr(regs)->ri = (val & 0xf);	\
-	regs->cr_iip = (val & ~0xfULL);		\
-})
-
-static inline unsigned long user_stack_pointer(struct pt_regs *regs)
-{
-	return regs->r12;
-}
-
-static inline int is_syscall_success(struct pt_regs *regs)
-{
-	return regs->r10 != -1;
-}
-
-static inline long regs_return_value(struct pt_regs *regs)
-{
-	if (is_syscall_success(regs))
-		return regs->r8;
-	else
-		return -regs->r8;
-}
-
-/* Conserve space in histogram by encoding slot bits in address
- * bits 2 and 3 rather than bits 0 and 1.
- */
-#define profile_pc(regs)						\
-({									\
-	unsigned long __ip = instruction_pointer(regs);			\
-	(__ip & ~3UL) + ((__ip & 3UL) << 2);				\
-})
-
-  /* given a pointer to a task_struct, return the user's pt_regs */
-# define task_pt_regs(t)		(((struct pt_regs *) ((char *) (t) + IA64_STK_OFFSET)) - 1)
-# define ia64_psr(regs)			((struct ia64_psr *) &(regs)->cr_ipsr)
-# define user_mode(regs)		(((struct ia64_psr *) &(regs)->cr_ipsr)->cpl != 0)
-# define user_stack(task,regs)	((long) regs - (long) task == IA64_STK_OFFSET - sizeof(*regs))
-# define fsys_mode(task,regs)					\
-  ({								\
-	  struct task_struct *_task = (task);			\
-	  struct pt_regs *_regs = (regs);			\
-	  !user_mode(_regs) && user_stack(_task, _regs);	\
-  })
-
-  /*
-   * System call handlers that, upon successful completion, need to return a negative value
-   * should call force_successful_syscall_return() right before returning.  On architectures
-   * where the syscall convention provides for a separate error flag (e.g., alpha, ia64,
-   * ppc{,64}, sparc{,64}, possibly others), this macro can be used to ensure that the error
-   * flag will not get set.  On architectures which do not support a separate error flag,
-   * the macro is a no-op and the spurious error condition needs to be filtered out by some
-   * other means (e.g., in user-level, by passing an extra argument to the syscall handler,
-   * or something along those lines).
-   *
-   * On ia64, we can clear the user's pt_regs->r8 to force a successful syscall.
-   */
-# define force_successful_syscall_return()	(task_pt_regs(current)->r8 = 0)
-
-  struct task_struct;			/* forward decl */
-  struct unw_frame_info;		/* forward decl */
-
-  extern unsigned long ia64_get_user_rbs_end (struct task_struct *, struct pt_regs *,
-					      unsigned long *);
-  extern long ia64_peek (struct task_struct *, struct switch_stack *, unsigned long,
-			 unsigned long, long *);
-  extern long ia64_poke (struct task_struct *, struct switch_stack *, unsigned long,
-			 unsigned long, long);
-  extern void ia64_flush_fph (struct task_struct *);
-  extern void ia64_sync_fph (struct task_struct *);
-  extern void ia64_sync_krbs(void);
-  extern long ia64_sync_user_rbs (struct task_struct *, struct switch_stack *,
-				  unsigned long, unsigned long);
-
-  /* get nat bits for scratch registers such that bit N==1 iff scratch register rN is a NaT */
-  extern unsigned long ia64_get_scratch_nat_bits (struct pt_regs *pt, unsigned long scratch_unat);
-  /* put nat bits for scratch registers such that scratch register rN is a NaT iff bit N==1 */
-  extern unsigned long ia64_put_scratch_nat_bits (struct pt_regs *pt, unsigned long nat);
-
-  extern void ia64_increment_ip (struct pt_regs *pt);
-  extern void ia64_decrement_ip (struct pt_regs *pt);
-
-  extern void ia64_ptrace_stop(void);
-  #define arch_ptrace_stop() \
-	ia64_ptrace_stop()
-  #define arch_ptrace_stop_needed() \
-	(!test_thread_flag(TIF_RESTORE_RSE))
-
-  #define arch_has_single_step()  (1)
-  #define arch_has_block_step()   (1)
-
-#endif /* !__ASSEMBLY__ */
-#endif /* _ASM_IA64_PTRACE_H */